Since a photographic method using a silver halide is superior to any other photographic methods such as an electro-photographic method or a diazo-photographic method in regard to photographic characteristics such as sensitivity and gradation adjustment, it has heretofore been utilized most widely in the technical field.
Recently, a technology of simply and rapidly obtaining a photographic image has been developed, by exchanging the conventional wet processing treatment (using a developer or the like in the method for forming a photographic image in a silver halide-containing photographic material) for a dry processing treatment by heating or the like.
As a means of obtaining a color image by heat-development, various methods have been proposed. For instance, a method of forming a color image by coupling of an oxidation product of a developing agent and a coupler has been described in U.S. Pat. Nos. 3,531,286, 3,761,270, and 4,021,240, Belgian Patent 802,519, and Research Disclosure, pages 31 and 32 (September, 1975).
However, the proposed method has a drawback in that the color image to be formed is often turbid since an image of reduced silver and a color image are simultaneously formed in the exposed and heat-developed area.
In order to overcome the drawback, various methods have been proposed, such as: a method of imagewise forming or releasing a mobile (diffusive) dye by heating, followed by transferring the mobile dye to a dye-fixing element having a mordant with a solvent such as water; a method of transferring the mobile dye to a dye-fixing element with a high boiling point organic solvent; a method of transferring the mobile dye to a dye-fixing element with a hydrophilic heat solvent as incorporated into the element; and a method of transferring the mobile dye, which is a heat-diffusive or sublimable dye, to a dye-receiving element such as a support. Refer to U.S. Pat. Nos. 4,463,079, 4,474,867, 4,478,927, 4,507,380, 4,500,626 and 4,483,914; and JP-A-58-149046, JP-A-58-149047, JP-A-59-152440, JP-A-59-154445, JP-A-59-165054, JP-A-59-180548, JP-A-59-168439, JP-A-59-174832, JP-A-59-174833, JP-A-59-174834 and JP-A-59-174835 (the term "JP-A" as used herein means an "unexamined published Japanese patent application")
Where a hydrophilic binder is used in the dye-fixing layer of the dye-fixing element of such image forming methods, the element often curls to the dye-fixing layer under low humidity conditions. Therefore, in general, a backing layer consisting essentially of a hydrophilic binder is provided on the back surface of the element so as to attain curling balance in the element.
However, use of such a backing layer causes many problems. Namely, where plural dye-fixing elements, each having a hydrophilic low molecular compound, such as a base or a base precursor in the dye-fixing layer, are piled up under high humidity conditions, the base or base precursor would migrate to the adjacent backing layer so that the distribution of the base or base precursor in the dye-fixing layer would become uneven. As a result, the color density of the developed and transferred image to be formed on the element would be uneven.